1. Field of the Invention
The present invention relates generally to medical methods and devices. In particular, the present invention relates to tissue anchors and methods for their use in fastening adjacent tissue layers in medical procedures.
Tissue approximation is useful in many medical procedures for a variety of purposes. In the broadest definition, tissue apposition may be performed by a number of conventional procedures, such as suturing, gluing, energy-mediated fusion, and the like. Of particular interest to the present invention, however, is the use of tissue fasteners which are positioned through penetrations in adjacent tissue layers and deployed to physically hold or anchor the tissue layers together.
A number of tissue-anchoring systems have been devised over the years. Many prior art tissue anchors include expandable cage structures, often referred to as malecotts, or “molybolts,” at opposite ends of a shaft, where the cages are expanded and deployed on each side of the layered tissues to be anchored together. One exemplary tissue anchor employing expandable structural elements on each side of a shaft for anchoring the esophagus to the stomach wall is described in commonly-owned, copending U.S. patent publication no. 2005/0228413. In some instances, the mechanical tissue fasteners may provide or define a central lumen or passage, typically to allow for drainage from one body lumen or cavity into another. Such fasteners are often referred to as “stents,” with an exemplary stent for draining a pseudocyst described in U.S. Pat. No. 6,620,122. The '122 stent has a barbell-like configuration with open cuffs at each end. The cuffs are not reinforced and do not provide significant strength for holding adjacent tissue structures together, particularly when the tissue structures tend to separate as the patient moves about.
While usable for many purposes, the tissue anchors of the prior art have often been either too rigid, providing good attachment but presenting substantial risk of tissue necrosis or adhesion, or too weak, presenting little risk of tissue damage but allowing leakage and movement at the point of tissue penetration.
Thus, for these reasons, it would be beneficial to provide alternative or improved tissue anchors and methods for their deployment and use, where the anchors can provide firm attachment of tissue while minimizing the risk of necrosis and other damage to the tissue. The tissue anchors should preferably be suitable for attachment both with and without a central lumen for fistula formation. The tissue anchors should be deliverable endoscopically to a wide variety of body lumens for a wide variety of purposes. Additionally, it would be desirable if the tissue anchors were removable, both during initial implantation procedures as well as in a subsequent procedure(s) many weeks, months, or even years following the initial implantation. At least some of these objectives will be met by the inventions described hereinbelow.
2. Description of the Background Art
US 2003/069533 describes an endoscopic transduodenal biliary drainage system which is introduced through a penetration, made by a trans-orally advanced catheter having a needle which is advanced from the duodenum into the gall bladder. U.S. Pat. No. 6,620,122 describes a system for placing a self-expanding stent from the stomach into a pseudocyst using a needle and an endoscope. US 2005/0228413, commonly assigned with the present application, describes a tissue-penetrating device for endoscopy or endosonography-guided (ultrasonic) procedures where an anchor may be placed to form an anastomosis between body lumens, including the intestine, stomach, and gallbladder. See also U.S. Pat. No. 5,458,131; U.S. Pat. No. 5,495,851; U.S. Pat. No. 5,944,738; U.S. Pat. No. 6,007,522; U.S. Pat. No. 6,231,587; U.S. Pat. No. 6,655,386; U.S. Pat. No. 7,273,451; U.S. Pat. No. 7,309,341; US 2004/0243122; US 2004/0249985; US 2007/0123917; WO 2006/062996; EP 1314404 Kahaleh et al. (2006) Gastrointestinal Endoscopy 64:52-59; and Kwan et al. (2007) Gastrointestinal Endoscopy 66:582-586.